Path: utzoo!utgpu!attcan!uunet!super!udel!gatech!bloom-beacon!think!ames!lll-tis!afit-ab!wbralick
From: wbralick@afit-ab.arpa (William A. Bralick)
Newsgroups: comp.sys.amiga
Subject: Re: Viruses (was: Re: The ultimate fix!!!)
Message-ID: <628@afit-ab.arpa>
Date: 11 Oct 88 00:02:47 GMT
References: <8810062045.AA04638@cory.Berkeley.EDU> <12643@oberon.USC.EDU>
Reply-To: wbralick@blackbird.afit.af.mil (William A. Bralick)
Distribution: na
Organization: SKY U, OH
Lines: 37

In article <12643@oberon.USC.EDU> papa@pollux.usc.edu (Marco Papa) writes:
>In article <8810062045.AA04638@cory.Berkeley.EDU> dillon@CORY.BERKELEY.EDU (Matt Dillon) writes:

[ conserving bandstand ... ]

>computer viruseshe is now developing.  One of ffirst results that he
>came up with was the proof of "undecidability" of whether a program is 
>a virus or not.  This means that I can give you the "source" of a program
>and there is no way for you to decide whether it will act as a virus or not.

Actually, this means that you cannot be *guarenteed* to be able to detect
*all* viruses.  This is not to say that the result is insignificant, just
that it is possible to decide that some programs are viruses, but provably
not all.

>As Matt pointed out, the only "secure" system is an isolated, un-changing
>system; one that would be of very little use to anybody.

Rather, it is a system which has excellent physical security, is 
electronically isolated, and has good-to-excellent configuration
management.  There are systems which have these characteristics
in the government (and elsewhere) which perform admirably accomplishing
the purpose for which they were built.  Note that this does not preclude
sabotage, etc.

>
>Virus detectors and "antidotes" are just temporary band-aids, until 
>"intelligent" virus writers develop viruses that we con't detect or figure
>out how they work.  That time is certainly not that far away.

I dunno, it is tantamount to trying to write a "false" program for which
no counterexample can be provided.  Goedel incompleteness tells us that
this is theoretically possible, but I'll be danged if I can figure out
how to write one.

Cordially,
Will